A heat treatment apparatus of this type includes a reaction tube, an adaptor for supporting the reaction tube, a nozzle for supplying treatment gas into the reaction tube, and a heater provided outside the reaction tube for heating the interior of the reaction tube, so that the heater heats up the interior of the reaction tube to a high temperature for treating a substrate. For example, in a treatment at a temperature higher than 1200° C., quarts cannot be used for the reaction tube or the nozzle. Therefore, SiC (silicon carbide) is used. However, since the SiC reaction tube becomes damaged due to temperature difference with the configuration of the SiC reaction tube, the reactor port cannot be formed of the SiC. Therefore, it is considered to form the reaction tube of SiC, and form the adapter of quartz (see Paragraph 0005, specification of Patent Document 1).
Patent Document 1: JP-A-9-97767